Homegrown New Hampshire host Emma Erler, lead horticulturist with Kirkwood Gardens, says “leave the leaves” and “save the stems” are great ideas for providing shelter for beneficial insects, particularly some species of solitary bees. But it’s also confusing.
When and how you tidy up garden stems can either create or destroy habitat for stem-nesting bees. And it’s actually something you need to consider in the fall.
Solitary bees create their nests in the spring and lay eggs; the larvae will develop into young adult bees, maybe overwintering in the nest before dispersing to start new nests the following spring.
To create maximum habitat for stem-nesting bees, trim stems back to leave a 12-24-inch stubble. As the foliage of the plant grows, it will help to make the stems less prominent.
If you cut stems after the first frost, the open stems will be ready and waiting for early spring bees searching for nest locations.
If you prefer to cut stems all the way to the ground, you can do it in the spring before new growth appears. This approach does not benefit stem-nesting bees, but it also doesn’t damage them.
You can also do nothing! An untrimmed, natural look is perfectly acceptable in the garden.
Prioritize leaving stems with good, hollow centers such as Joe-Pye weed, sunflowers, purple coneflower, beebalm, blackberries, raspberries, goldenrod, ironweed, elderberry, and others.
If you’re looking for more comprehensive information, check out this study.
If you have a gardening question for Homegrown NH, email or send a voice memo to HomegrownNH@ NHPR.org.
See you in the garden!
Homegrown New Hampshire is a collaboration between Squam Lakes Natural Science Center and NHPR.
